1. Field of the General Inventive Concept
The present general inventive concept relates to an image forming apparatus, and more particularly, to an image forming apparatus to enhance printing performance to reduce a total printing time by selecting a printing speed according to a remaining printing amount during switching between mono printing and color printing when a printing speed is different between the mono printing and the color printing, and a printing method of the image forming apparatus.
2. Description of the Related Art
Image forming apparatuses form an image on a recording medium based on printing data. An image forming apparatus capable of forming a color image forms an electrostatic latent image by scanning light onto a photoconductor body that is charged to a predetermined electric potential. The electrostatic latent image is coated with a developer of a predetermined color. A coated electrostatic latent image is transferred and fused to a recording medium so that a color image is formed.
An image forming apparatus capable of forming a color image may include a single-pass type image forming apparatus provided with a plurality of light scanning units (LSUs) and photoconductors corresponding to multiple colors and a multi-pass type image forming apparatus provided with one LSU and one photoconductor corresponding to multiple colors.
In a conventional multi-pass type image forming apparatus, a single LSU scans light beams corresponding to multiple colors, that is, yellow (Y), magenta (M), cyan (C), and black (K), onto a photoconductor. Images formed on the photoconductor are sequentially transferred to an intermediary transfer medium.
A recording medium is picked up by a pickup roller before all images are transferred to the intermediary transfer medium. The images transferred to the intermediary transfer medium are transferred to a recording medium by a transfer roller. The images transferred to the recording medium are fused by a fusing roller and thus image forming is completed.
However, for mono printing in a multi-pass type image forming apparatus, only black color is scanned onto a photoconductor. When an image formed on the photoconductor is transferred to the recording medium via the intermediary transfer medium, the image is printed in a manner like a single-pass type unlike color printing.
When a printing speed in an image forming apparatus is different between mono printing and color printing, if mono printing is switched to color printing or vice versa, a preliminary operation to change the printing speed is necessarily performed. That is, when the printing speed is different between mono printing and color printing, a predetermined time is used to set an LSU motor clock and a main motor clock suitable for each printing speed whenever mono printing is switched to color printing or vice versa.
As such, when the printing speed in an image forming apparatus is different between mono printing and color printing, for a printing job in which switching between mono printing and color printing frequently occurs, a considerable time may be used for printing due to an intermediary operation according to the switching between the mono printing and color printing.
To reduce the unnecessary time used during printing, when printing with a relatively slow printing speed is switched to printing with a relatively fast printing speed, printing may be performed at the previous slower printing speed without performing an operation to change the printing speed. However, when an amount of printing that is performed without increasing the printing speed is larger than a predetermined number of print sheets, it may be advantageous for the total printing time to change the printing speed to the faster printing speed.